Presently television broadcasters occasionally transmit to their viewers auxiliary information in the form of messages which are displayed on the viewers' television receivers as alpha-numeric data which usually horizontally scrolls across the television receiver screen, generally near the bottom thereof. These auxiliary messages are only transmitted infrequently such as to notify viewers of fast-breaking news items of general interest or of programming changes, such as a delay in the start of an upcoming program. The present use of this method to convey information to viewers is thus minimal.
This, of course, is in part due to the fact that viewers would generally find an excessive amount of such auxiliary messages distasteful, being of interest only to some and to many very distracting from the programs they are watching.
In order to avoid disturbing viewers not interested in the auxiliary messages, they may be transmitted in a coded fashion as, for example, by intensity modulating a small area of the television screen with a viewer employing a decoder to decode the intensity modulated message. The transmitted auxiliary message appears on the television screen as a small bright spot. Such a system is described in U.S. Pat. No. 3,993,861 for a "Digital Video Modulation and Demodulation System" assigned to the assignee of the present application and incorporated herein by reference. This system, while presenting messages with minimum distraction to the viewer, is limited in that the viewer does not have any control over the specifics of the messages which he receives and processes. For example, if all news, sports, weather and stock market information is so broadcast, a user is burdened by the requirement of receiving all such information when, in fact, he may only be interested in receiving weather reports or stock market prices. Furthermore, such a system does not provide for display of such messages on the television receiver the user is watching but rather requires some additional equipment to utilize the coded messages.